1. Technical Field
The present invention relates to an electric wire holding structure and an electric wire holding method for holding a plurality of electric wires.
2. Background Art
Conventionally, there has been an electric wire holding structure including a plurality of electric wires each of which is provided, at an end thereof, with a conductive part having a rectangular outer shape in a section perpendicular to an extending direction of the electric wires, wherein a plurality of the electric wires are bonded together by welding the rectangular conductive parts of the respective electric wires with ultrasonic vibration. More specifically, this electric wire holding structure is so constructed that the conductive parts which are formed in a rectangular shape having substantially the same size are aligned in both vertical and lateral directions, to be bonded together by welding.
By the way, in case where a vibrating direction of ultrasonic waves is parallel to the faces to be bonded, the bonding faces which are parallel to the vibrating direction vibrate adjacent faces relative to each other, thereby to transmit the vibration. Therefore, the ultrasonic vibration is likely to be damped under influence of the bonding faces which are parallel to the vibrating direction. For this reason, as goes apart from an ultrasonic horn which is an ultrasonic vibration generating source, the ultrasonic vibration is likely to be damped.
On the other hand, in case where the vibrating direction of the ultrasonic waves is perpendicular to the bonding faces, the ultrasonic vibration is unlikely to be damped even at a position separated from the ultrasonic horn, because the bonding faces are vibrated in the vibrating direction to transmit the vibration.
Accordingly, although in a region where the conductive parts are bonded on a plane which is perpendicular to the vibrating direction of the ultrasonic waves, a bonding strength is unlikely to be deteriorated even at a position separated from the ultrasonic horn, in a region where the conductive parts are bonded on a plane which is parallel to the vibrating direction of the ultrasonic waves, the bonding strength is likely to be deteriorated at the position separated from the ultrasonic horn.
Under the circumstances, there has been employed such an electric wire holding method that the ultrasonic vibration is applied again to a plurality of electric wires which have been aligned in both vertical and lateral directions and bonded together by welding, from a position rotated by 90 degree, thereby to prevent deterioration of the bonding strength of the electric wires in both the vertical and lateral directions.
Moreover, an electric wire holding method for preventing deterioration of the bonding strength of a plurality of electric wires is disclosed in JP-A-2007-185706.
In the electric wire holding method disclosed in JP-A-2007-185706, in a state where core wires of two of a plurality of electric wires are clamped between a pair of dies, ultrasonic vibration is applied to one of the dies thereby to bond the core wires of the two electric wires to each other. Thereafter, the core wires of the other electric wires are superposed on a first bonded core wire bundle composed of the bonded core wires of the two electric wires, one by one. Every time the core wires are superposed one by one, in a state where the first bonded core wire bundle and the core wires of the other electric wires which are superposed on the first bonded core wire bundle are clamped between a pair of the dies, the ultrasonic vibration is applied to one of the dies, thereby to bond the core wires of the other electric wires to the first bonded core wire bundle, one by one.